JP3707321B2 - Color printing apparatus and printing method using vertical array head, and print head therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for performing color printing using a print head for forming a plurality of color dots.
[0002]
[Prior art]
Examples of the printing apparatus that records dots while the print head scans in the main scanning direction and the sub-scanning direction include a serial scan printer and a drum scan printer. As one of techniques for improving image quality in this type of printer, particularly an ink jet printer, an “interlace method” disclosed in US Pat. No. 4,198,642, Japanese Patent Application Laid-Open No. 53-2040, and the like. There is a technology called.
[0003]
FIG. 27 is an explanatory diagram showing an example of an interlace method. In this specification, the following parameters are used as parameters for defining the printing method.
[0004]
N: Number of nozzles [pieces]
k: Nozzle pitch [dot],
s: number of scan repetitions,
D: Nozzle density [piece / inch],
L: Sub-scan feed amount [dot] or [inch],
w: Dot pitch [inch].
[0005]
The number N of nozzles is the number of nozzles used for forming dots. In the example of FIG. 27, N = 3. The nozzle pitch k [dot] indicates how many nozzle pitches (dot pitch w) the center point interval of the nozzles in the print head is. In the example of FIG. 27, k = 2. The number of scan repetitions s [times] is a number indicating how many main scans each main scan line is filled with dots. Hereinafter, the main scanning line is referred to as “raster”. In the example of FIG. 27, since each raster is filled by one main scan, s = 1. As will be described later, when s is 2 or more, dots are intermittently formed along the main scanning direction. The nozzle density D [pieces / inch] indicates how many nozzles are arranged per inch in the nozzle array of the print head. The sub-scan feed amount L [dot] or [inch] indicates the distance moved by one sub-scan. The dot pitch w [inch] is the dot pitch in the printed image. In general, w = 1 / (D · k) and k = 1 / (D · w) are established.
[0006]
In FIG. 27, circles including two-digit numbers indicate dot recording positions. As shown in the legend at the lower left of FIG. 27, among the two-digit numbers in the circle, the number on the left indicates the nozzle number, and the number on the right indicates the printing order (the number of times of main scanning) ).
[0007]
The interlace method shown in FIG. 27 is characterized by the configuration of the nozzle array of the print head and the sub-scanning method. That is, in the interlace method, the nozzle pitch k indicating the interval between the center points of adjacent nozzles is set to an integer of 2 or more, and the number of nozzles N and the nozzle pitch k are selected to be integers that are relatively prime to each other. The sub-scan feed amount L is set to a constant value given by N / (D · k).
[0008]
This interlace method has an advantage that variations in nozzle pitch, ink ejection characteristics, and the like can be dispersed on a printed image. Therefore, even if there are variations in the nozzle pitch and ejection characteristics, it is possible to alleviate these effects and improve the image quality.
[0009]
As another technique aiming at image quality improvement in a color inkjet printer, there is a technique called “overlap method” or “multi-scan method” disclosed in Japanese Patent Laid-Open No. 3-207665, Japanese Patent Publication No. 4-19030, and the like. .
[0010]
FIG. 28 is an explanatory diagram showing an example of the overlap method. In this overlap method, eight nozzles are classified into two sets of nozzle groups. The first group of nozzles is composed of four nozzles having an even number of nozzle numbers (the number on the left side in the circle), and the second group of nozzles is composed of four nozzles having an odd number of nozzles. It consists of a nozzle. In one main scan, dots are formed every (s-1) dots in the main scan direction by driving each set of nozzle groups at intermittent timing. In the example of FIG. 28, since s = 2, dots are formed every other dot. The drive timing of each group of nozzle groups is controlled so that dots are formed at different positions in the main scanning direction. That is, as shown in FIG. 28, the nozzles of the first nozzle group (nozzle numbers 8, 6, 4, 2) and the nozzles of the second nozzle group (nozzle numbers 7, 5, 3, 1) are The recording position is shifted by one dot pitch in the main scanning direction. Such main scanning is performed a plurality of times, and the drive timing of each nozzle group is shifted each time, thereby completing the formation of all dots on the raster.
[0011]
Also in the overlap method, the nozzle pitch k is set to an integer of 2 or more, as in the interlace method. However, the number of nozzles N and the nozzle pitch k are not relatively prime. Instead, the value N / s obtained by dividing the number of nozzles N by the number of scan repetitions s and the nozzle pitch k are relatively prime. It is chosen as an integer. The sub-scan feed amount L is set to a constant value given by N / (s · D · k). Note that “integers A and B are relatively prime” means that the integers A and B have no common divisor other than 1.
[0012]
In this overlap method, dots on each raster are not recorded by the same nozzle, but are recorded using a plurality of nozzles. Therefore, even when there are variations in nozzle characteristics (pitch, ejection characteristics, etc.), it is possible to prevent the influence of specific nozzle characteristics from affecting one entire raster, and as a result, image quality can be improved. .
[0013]
[Problems to be solved by the invention]
By the way, a printing method preferable in terms of improving image quality differs depending on the arrangement of nozzle arrays in the print head. Therefore, it may not be easy to set a printing method for improving image quality for a specific print head.
[0014]
The present invention has been made to solve the above-described problems in the prior art, and an object thereof is to provide a technique capable of obtaining high image quality with respect to a specific print head.
[0015]
[Means for solving the problems and their functions and effects]
In order to solve at least a part of the above-described problems, in the present invention, the first sub-scanning drive mechanism that performs sub-scan feed with relatively high accuracy and the sub-scan feed by at least the first sub-scan drive mechanism have been completed. Later, a sub-scanning drive unit including a second sub-scanning drive mechanism that performs sub-scan feed with relatively low accuracy is used. The print head includes at least a yellow dot forming element group for forming yellow dots. To form dots of different colors A plurality of dot forming element groups including a first dot forming element array arranged in a predetermined order along the sub-scanning direction is used. In this first dot forming element array, For color printing The arrangement order of the plurality of dot forming element groups is determined so that yellow dots are formed after other dots at an arbitrary position on the print medium. In addition, the plurality of dot formation element groups respectively have the same number of dot formation elements. In the print head, a plurality of dot forming elements are arranged so that yellow dots are formed after black dots, magenta dots, and cyan dots at arbitrary positions on the print medium during color printing. For color printing, The formation of black dots, magenta dots, and cyan dots on the printing medium is completed while sub-scan feed is executed with relatively high accuracy using both the first and second sub-scan driving mechanisms. Also, Trailing edge of print media When the sub-scan feed is executed only by the second sub-scanning drive mechanism after passing the nipping point of the first sub-scanning drive mechanism, the formation of black dots, magenta dots, and cyan dots is completed, and yellow In an area where dot formation has not been completed Printing is executed using only the dot formation elements included in the yellow dot formation element group among the dot formation elements included in the first dot formation element array.
[0016]
In the present invention, only the dot forming element for yellow dots is used in the first dot forming element array in the vicinity of the rear end of the printing medium. In the vicinity of the rear end of the print medium, the sub-scan feed is not performed by the first sub-scanning drive mechanism, and the sub-scan feed is performed by the second sub-scanning drive mechanism, so that the feed accuracy is relatively low. However, since the yellow dots are relatively inconspicuous, even if the sub-scan feed accuracy is low, the image quality does not deteriorate much. As described above, according to the present invention, it is possible to execute printing that provides high image quality for a specific print head.
[0017]
The rear edge of the print medium When the sub-scan feed is executed only by the second sub-scanning drive mechanism after passing the clamping point of the first sub-scanning drive mechanism, Trailing edge of print media Passes the clamping point of the first sub-scanning drive mechanism The second sub-scanning drive mechanism may be caused to execute the sub-scan feed with the same feed amount as when the first sub-scan driving mechanism is executed at the previous position.
[0018]
In this way, the printing process can be continued without changing the sub-scan feed, so that the control for scanning can be simplified.
[0019]
The print head further includes a black dot forming element group for forming black dots, is formed in parallel with the first dot forming element array, and precedes the first dot forming element array. You may make it provide the 2nd dot formation element array which can form a dot on the said printing medium. The black dot formation element group may include at least a plurality of dot formation elements arranged at the same sub-scanning position as the dot formation elements included in the plurality of dot formation element groups in the first dot formation element array. Good. During color printing, with respect to black dots, specific chromatic color dot formation that enables dot formation on the printing medium earliest among the plurality of dot formation element groups in the first dot formation element array Black dots are formed using only dot forming elements existing at the same sub-scanning position as the dot forming elements used in the element group.
[0020]
In this way, since black dots are formed earlier than dots of other colors at each position on the print medium, it is possible to prevent bleeding of the black dots and obtain a color image with high saturation. .
[0021]
The first and second dot formation element arrays are preferably formed in the same actuator.
[0022]
By so doing, it is possible to arrange the dot forming elements with high accuracy, so that the image quality can be improved.
[0023]
The print head according to the present invention has a first dot formation in which a plurality of dot formation element groups including at least yellow dot formation element groups for forming yellow dots are arranged in a predetermined order along a predetermined sub-scanning direction. It has an element array. The plurality of dot forming element groups respectively have the same number of dot forming elements, and the yellow dot forming element group is arranged at the end of the first dot forming element array.
[0024]
When such a print head is used, yellow dots can be formed after other dots are formed in the vicinity of the edge of the print medium. Since yellow dots are not conspicuous, even when the sub-scan feed accuracy is low in the vicinity of the edge of the print medium, the image quality does not deteriorate much.
[0025]
Note that the first and second dot formation element arrays may each include the same number of dot formation element groups for forming dots of different colors.
[0026]
In this way, it is possible to form a large number of dots with a small number of arrays.
[0027]
Alternatively, the second dot formation element array may include black dot formation elements arranged at the same sub-scanning position as the dot formation elements included in the first dot formation element array.
[0028]
In this way, it is possible to print at high speed using a large number of black dot forming elements during monochrome printing.
[0029]
As specific modes of the present invention, various modes such as a printing apparatus, a printing method, a recording medium, and a print head can be taken.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
A. Overall configuration of the device:
Next, embodiments of the present invention will be described based on examples. FIG. 1 is a schematic perspective view showing a main configuration of a color inkjet printer 20 as an embodiment of the present invention. The printer 20 includes a paper stacker 22, a paper feed roller 24 driven by a step motor (not shown), a platen plate 26, a carriage 28, a step motor 30, and a traction belt 32 driven by the step motor 30. And a guide rail 34 for the carriage 28. A print head 36 having a large number of nozzles is mounted on the carriage 28.
[0031]
The printing paper P is taken up by the paper feed roller 24 from the paper stacker 22 and fed on the surface of the platen plate 26 in the sub-scanning direction. The carriage 28 is pulled by a pulling belt 32 driven by a step motor 30 and moves in the main scanning direction along the guide rail 34. The main scanning direction is perpendicular to the sub-scanning direction.
[0032]
FIG. 2 is a block diagram showing an electrical configuration of the printer 20. The printer 20 includes a reception buffer memory 50 that receives a signal supplied from the host computer 100, an image buffer 52 that stores print data, and a system controller 54 that controls the operation of the entire printer 20. The system controller 54 is connected to a main scanning drive driver 61 that drives the carriage motor 30, a sub-scanning drive driver 62 that drives the paper feed motor 31, and a head drive driver 63 that drives the print head 36.
[0033]
A printer driver (not shown) of the host computer 100 determines various parameter values that define the printing operation based on a printing method (described later) designated by the user. The printer driver further generates print data for performing printing in the printing method based on these parameter values, and transfers the print data to the printer 20. The transferred print data is temporarily stored in the reception buffer memory 50. In the printer 20, the system controller 54 reads necessary information from print data from the reception buffer memory 50, and sends control signals to the drivers 61, 62, and 63 based on the information.
[0034]
The image buffer 52 stores image data of a plurality of color components obtained by separating the print data received by the reception buffer memory 50 for each color component. The head drive driver 63 reads the image data of each color component from the image buffer 52 in accordance with a control signal from the system controller 54 and drives the nozzle array of each color provided in the print head 36 in accordance with this.
[0035]
B. Print head configuration:
FIG. 3 is an explanatory diagram showing the arrangement of nozzles formed on the bottom surface of the actuator 40 provided below the print head 36. On the bottom surface of the actuator 40, a color nozzle row and a black nozzle row arranged on a straight line along the sub-scanning direction are formed. The “actuator” means an ink discharge mechanism including a nozzle and a drive element (for example, a piezo element or a heater) for discharging ink. Usually, the nozzle portion of one actuator is integrally formed by ceramic molding. If two nozzle rows are formed in one actuator, the nozzles can be arranged with high accuracy, and the image quality can be improved. In the present specification, the “nozzle row” is also referred to as a “nozzle array”.
[0036]
The black nozzle row has 48 nozzles # K1 to # K48. These nozzles # K1 to # K48 are arranged at a constant nozzle pitch k along the sub-scanning direction. This nozzle pitch k is 6 dots. However, the nozzle pitch k can be set to a value obtained by multiplying the dot pitch on the print medium P by an arbitrary integer of 2 or more.
[0037]
The color nozzle row includes a yellow nozzle group 40Y, a magenta nozzle group 40M, and a cyan nozzle group 40C. In this specification, the nozzle group for chromatic ink is also referred to as a “chromatic nozzle group”. The yellow nozzle group 40Y has fifteen nozzles # Y1 to # Y15, and the pitch of these fifteen nozzles is the same as the nozzle pitch k of the black nozzle row. The same applies to the magenta nozzle group 40M and the cyan nozzle group 40C. The “x” mark between the nozzle # Y15 at the lower end of the yellow nozzle group 40Y and the nozzle # M1 at the upper end of the magenta nozzle group 40M indicates that no nozzle is formed at that position. ing. Accordingly, the interval between the nozzle # Y15 at the lower end of the yellow nozzle group 40Y and the nozzle # M1 at the upper end of the magenta nozzle group 40M is twice the nozzle pitch k. The same applies to the interval between the nozzle # M15 at the lower end of the magenta nozzle group 40M and the nozzle # C1 at the upper end of the cyan nozzle group 40C. In other words, the intervals between the yellow, magenta, and cyan nozzle groups are set to a value twice the nozzle pitch k.
[0038]
The nozzles of the color nozzle groups 40Y, 40M, and 40C are arranged at the same sub-scanning position as the nozzles of the black nozzle row 40K. However, among the 48 nozzles # K1 to # K48 in the black nozzle row 40K, the chromatic ink is located at the corresponding position for the 16th, 32nd and 48th nozzles # K16, # K32, and # K48. No nozzle is provided.
[0039]
During printing, ink droplets are ejected from each nozzle while the print head 36 is moving in the main scanning direction together with the carriage 28 (FIG. 1). However, depending on the printing method, not all nozzles are always used, and only some nozzles may be used.
[0040]
C. Sub-scanning drive mechanism configuration:
FIG. 4 is a conceptual diagram showing a sub-scan driving unit that conveys the printing paper P. The sub-scanning drive unit includes a first sub-scanning drive mechanism 25 provided on the paper feed side and a second sub-scanning drive mechanism 27 provided on the paper discharge side. The first sub-scanning drive mechanism 25 includes a paper feed roller 25a and a driven roller 25b. The second sub-scanning drive mechanism 27 includes a paper discharge roller 27a and a jagged roller 27b. These rollers 25a, 25b, 27a, 27b are driven by the rotation of the paper feed motor 31 (FIG. 2) being transmitted through a gear train (not shown). At the start of printing, the printing paper P is sandwiched between the rollers 25a and 25b of the first sub-scanning drive mechanism 25 from the paper supply side (the right side in FIG. 4) and conveyed by the rotation of both rollers. When the leading edge of the printing paper P is sandwiched between the rollers 27a and 27b of the second sub-scanning drive mechanism 27, these rollers are also sent to the paper discharge side. In addition, after the trailing edge of the printing paper P has passed the pinching point of the first sub-scanning drive mechanism 25 (the point pinched by the rollers 25a and 25b), the printing paper P is printed only by the second sub-scanning driving mechanism 27. Is transported. An image is recorded on the printing paper P by the print head 36 on the platen 26.
[0041]
In this printer, the paper feeding accuracy of the first sub-scanning drive mechanism 25 on the paper feed side is higher than that of the second sub-scanning drive mechanism 27 on the paper discharge side. Therefore, when the paper feed is performed only by the second sub-scanning drive mechanism 27 after the trailing edge of the printing paper P has passed the clamping point of the first sub-scanning drive mechanism 25, the accuracy of the feed amount is the first. This is lower than the case of being transported by one sub-scanning drive mechanism 25.
[0042]
In FIG. 4, the symbol “40W” indicates the full width of the nozzle row along the sub-scanning direction, and the symbol “WLP” indicates the width of the yellow nozzle group 40Y. Note that the width WLP corresponds to the width of a low-accuracy region described later. The symbol “WB” indicates the distance from the clamping point of the first sub-scanning drive mechanism 25 to the rear end of the nozzle row. In the present specification, the leading edge and the trailing edge of the printing paper or nozzle row are defined according to the paper feeding direction (sub-scanning direction). The paper feed direction and the sub-scanning direction are defined as directions in which the printing paper P moves relative to the printer 20 during sub-scanning. The “front end” may be referred to as “upper end”, and the “rear end” may be referred to as “lower end”.
[0043]
D. Basic conditions for general printing methods:
Before describing the printing method in the embodiment of the present invention, first, basic conditions required for a general printing method will be described first. In the following description, “printing method” is referred to as “dot recording method”.
[0044]
FIG. 5 is an explanatory diagram for illustrating basic conditions of a general dot recording method when the scan repetition number s is 1. FIG. FIG. 5A shows an example of sub-scan feed when four nozzles are used, and FIG. 5B shows the parameters of the dot recording method. In FIG. 5A, solid line circles including numbers indicate the positions in the sub-scanning direction of the four nozzles after each sub-scan feed. Numbers 0 to 3 in the circles indicate nozzle numbers. The positions of the four nozzles are sent in the sub-scanning direction every time one main scanning is completed. In practice, however, feeding in the sub-scanning direction is realized by moving the paper by the paper feed motor 31 (FIG. 2).
[0045]
As shown at the left end of FIG. 5A, in this example, the sub-scan feed amount L is a constant value of 4 dots. Accordingly, every time the sub-scan feed is performed, the positions of the four nozzles are shifted in the sub-scanning direction by 4 dots. When the scan repetition number s is 1, each nozzle can record all the dots (also referred to as “pixels”) on the respective raster. At the right end of FIG. 5A, the number of the nozzle that records dots on each raster is shown. Note that in the raster drawn with a broken line extending in the right direction (main scanning direction) from the circle indicating the position of the nozzle in the sub-scanning direction, at least one of the upper and lower rasters cannot be recorded. Is done. On the other hand, the raster drawn with a solid line extending in the main scanning direction is a range in which the previous and subsequent rasters can be recorded as dots. The range in which recording can actually be performed in this way is hereinafter referred to as an effective recording range (effective printing range) or a “printing area”.
[0046]
FIG. 5B shows various parameters relating to this dot recording method. The parameters of the dot recording method include nozzle pitch k [dots], number of used nozzles N [pieces], number of scan repetitions s, number of effective nozzles Neff [pieces], and sub-scan feed amount L [dots]. include.
[0047]
In the example of FIG. 5, the nozzle pitch k is 3 dots. The number of used nozzles N is four. The number N of used nozzles is the number of nozzles actually used among the plurality of mounted nozzles. The number of scan repetitions s means that dots are intermittently formed every (s-1) dots in one main scan. Therefore, the scan repetition number s is also equal to the number of nozzles used to record all dots on each raster. In the case of FIG. 5, the scan repetition number s is 1. The effective nozzle number Neff is a value obtained by dividing the used nozzle number N by the scan repetition number s. This effective nozzle number Neff can be considered to indicate the net number of rasters that can be recorded in one main scan. The meaning of the effective nozzle number Neff will be further described later.
[0048]
The table in FIG. 5B shows the sub-scan feed amount L, the cumulative value ΣL, and the nozzle offset F after each sub-scan feed for each sub-scan feed. Here, the offset F refers to the position after the sub-scan feed when the periodic position of the first nozzle that is not subjected to the sub-scan feed (in FIG. 5, every fourth dot position) is the reference position of the offset 0. This is a value indicating how many dots the nozzle position is away from the reference position in the sub-scanning direction. For example, as shown in FIG. 5A, the first sub-scan feed moves the nozzle position in the sub-scan direction by the sub-scan feed amount L (4 dots). On the other hand, the nozzle pitch k is 3 dots. Therefore, the nozzle offset F after the first sub-scan feed is 1 (see FIG. 5A). Similarly, the nozzle position after the second sub-scan feed is moved by ΣL = 8 dots from the initial position, and its offset F is 2. The nozzle position after the third sub-scan feed is moved by ΣL = 12 dots from the initial position, and the offset F is zero. Since the nozzle offset F returns to 0 by three sub-scan feeds, all the dots on the raster in the effective recording range can be recorded by repeating this cycle with three sub-scans as one cycle. .
[0049]
As can be seen from the above example, when the position of the nozzle is away from the initial position by an integral multiple of the nozzle pitch k, the offset F is zero. The offset F is given by the remainder (ΣL)% k obtained by dividing the cumulative value ΣL of the sub-scan feed amount L by the nozzle pitch k. Here, “%” is an operator indicating that the remainder of division is taken. If the initial position of the nozzle is considered as a periodic position, the offset F can be considered to indicate a phase shift amount from the initial position of the nozzle.
[0050]
When the number of scan repetitions s is 1, the following conditions must be satisfied in order to prevent missing or overlapping rasters in the effective recording range.
[0051]
Condition c1: The number of sub-scan feeds in one cycle is equal to the nozzle pitch k.
[0052]
Condition c2: Nozzle offset F after each sub-scan feed in one cycle is a different value in the range of 0 to (k−1).
[0053]
Condition c3: The sub-scan average feed amount (ΣL / k) is equal to the number N of used nozzles. In other words, the cumulative value ΣL of the sub-scan feed amount L per cycle is equal to a value (N × k) obtained by multiplying the number of used nozzles N and the nozzle pitch k.
[0054]
Each of the above conditions can be understood by thinking as follows. Since there are (k-1) rasters between adjacent nozzles, recording is performed on these (k-1) rasters in one cycle, and the nozzle reference position (position where the offset F is zero). In order to return to, the number of sub-scan feeds in one cycle is k times. If the number of sub-scan feeds in one cycle is less than k times, the recorded raster will be lost. On the other hand, if the number of sub-scan feeds in one cycle is greater than k times, the recorded rasters will overlap. Therefore, the first condition c1 is satisfied.
[0055]
When the number of sub-scan feeds in one cycle is k times, only when the offset F value after each sub-scan feed is a different value in the range of 0 to (k-1), missing or overlapping rasters are recorded. Disappears. Therefore, the second condition c2 is satisfied.
[0056]
If the first and second conditions are satisfied, each of the N nozzles records k rasters in one cycle. Therefore, N × k rasters are recorded in one cycle. On the other hand, if the third condition c3 is satisfied, as shown in FIG. 5A, the nozzle position after one cycle (after k sub-scan feeds) is N × k from the initial nozzle position. Comes to a raster away position. Therefore, by satisfying the first to third conditions c1 to c3, it is possible to eliminate omissions and overlaps in the recorded raster in the range of these N × k rasters.
[0057]
FIG. 6 is an explanatory diagram for illustrating basic conditions of a general dot recording method when the number of scan repetitions s is 2 or more. When the scan repetition number s is 2 or more, the same raster is recorded by s different nozzles. Hereinafter, a dot recording method in which the scan repetition number s is 2 or more is referred to as an “overlap method”.
[0058]
The dot recording method shown in FIG. 6 is obtained by changing the scan repetition number s and the sub-scan feed amount L among the parameters of the dot recording method shown in FIG. As can be seen from FIG. 6A, the sub-scan feed amount L in the dot recording method of FIG. 6 is a constant value of 2 dots. However, in FIG. 6A, the position of the nozzle after the odd-numbered sub-scan feed is indicated by a rhombus. As shown at the right end of FIG. 6A, the pixel position recorded after the odd-numbered sub-scan feed is the same as the pixel position recorded after the even-numbered sub-scan feed and one dot in the main scanning direction. It is off. Therefore, a plurality of dots on the same raster are intermittently recorded by two different nozzles. For example, the uppermost raster in the effective recording range is intermittently recorded every other dot by the second nozzle after the first sub-scan feed, and then 1 by the zeroth nozzle after the fourth sub-scan feed. Recorded intermittently every other dot. In general, in the overlap method, each nozzle is driven at an intermittent timing so that (s-1) dot recording is prohibited after one dot is recorded during one main scan.
[0059]
In the overlap method, it is only necessary that the positions in the main scanning direction of a plurality of nozzles that record the same raster are shifted from each other. Therefore, the actual shift amount in the main scanning direction at each main scanning is shown in FIG. Various things other than those shown in FIG. For example, after the first sub-scan feed, a dot at a position indicated by a circle is recorded without performing a shift in the main scan direction, and after a fourth sub-scan feed, a shift in the main scan direction is performed and a position indicated by a rhombus It is also possible to record the dots.
[0060]
At the bottom of the table in FIG. 6B, the value of the offset F after each sub-scan in one cycle is shown. One cycle includes six sub-scan feeds, and the offset F after each sub-scan feed from the first to sixth times includes a value in the range of 0 to 2 twice. Further, the change in the offset F after the third sub-scan feed from the first time to the third time is equal to the change in the offset F after the third sub-scan feed from the fourth time to the sixth time. As shown at the left end of FIG. 6 (A), six sub-scan feeds in one cycle can be divided into two sets of three small cycles. At this time, one cycle of the sub-scan feed is completed by repeating the small cycle s times.
[0061]
In general, when the scan repetition number s is an integer of 2 or more, the first to third conditions c1 to c3 described above are rewritten as the following conditions c1 ′ to c3 ′.
[0062]
Condition c1 ′: The number of sub-scan feeds in one cycle is equal to a value (k × s) obtained by multiplying the nozzle pitch k and the scan repetition number s.
[0063]
Condition c2 ′: Nozzle offset F after each sub-scan feed in one cycle is a value in the range of 0 to (k−1), and each value is repeated s times.
[0064]
Condition c3 ′: The sub-scan average feed amount {ΣL / (k × s)} is equal to the effective nozzle number Neff (= N / s). In other words, the cumulative value ΣL of the sub-scan feed amount L per cycle is equal to a value {Neff × (k × s)} obtained by multiplying the effective nozzle number Neff and the sub-scan feed number (k × s).
[0065]
The above conditions c1 ′ to c3 ′ are also satisfied when the scan repetition number s is 1. Therefore, the conditions c1 ′ to c3 ′ are conditions that are generally satisfied for the dot recording method regardless of the value of the scan repetition number s. That is, if the above three conditions c1 ′ to c3 ′ are satisfied, it is possible to prevent the recorded dots from being missing or overlapping in the effective recording range. However, in the case of employing the overlap method (when the scan repetition number s is 2 or more), it is also necessary to have a condition that the recording positions of the nozzles that record the same raster are shifted in the main scanning direction.
[0066]
Depending on the recording method, partial overlap may be performed. “Partial overlap” refers to a recording method in which a raster recorded by one nozzle and a raster recorded by a plurality of nozzles are mixed. Even in such a recording method using partial overlap, the effective nozzle number Neff can be defined. For example, in a partial overlap method in which two nozzles of four nozzles cooperate to record the same raster, and the remaining two nozzles each record one raster, The effective nozzle number Neff is three. Even in the case of such a partial overlap method, the above-described three conditions c1 ′ to c3 ′ are satisfied.
[0067]
Note that the effective nozzle number Neff can be considered to indicate the net number of rasters that can be recorded in one main scan. For example, when the number of scan repetitions s is 2, a number of rasters equal to the number of used nozzles N can be recorded in two main scans, so the net of rasters that can be recorded in one main scan Is equal to N / s (ie, Neff).
[0068]
E. First embodiment of the printing method:
FIG. 7 is an explanatory diagram showing scanning parameters in the printing method of the first embodiment of the present invention. In the first embodiment, the nozzle pitch k is 6 dots, the scan repetition number s is 1, the number of used nozzles N is 13, and the effective nozzle number Neff is 13.
[0069]
The table at the bottom of FIG. 7 shows parameters relating to the first to seventh passes. In the present specification, one main scan is also referred to as “pass”. In this table, for each pass, the sub-scan feed amount L executed immediately before the pass, the accumulated value ΣL, and the offset F are shown. The sub-scan feed amount L is a constant value of 13 dots. A printing method (scanning method) in which the sub-scan feed amount L is constant is called “regular feed”. Note that the scanning parameters of the first embodiment satisfy the above-described conditions c1 ′ to c3 ′.
[0070]
FIG. 8 is an explanatory diagram showing nozzles used in the first embodiment. The actuator 40 of FIG. 8 is the same as that shown in FIG. 3, but only some of the nozzles are used in the first embodiment. In FIG. 8, the nozzles used in the first embodiment are indicated by white circles, while the nozzles not used are indicated by black circles. That is, for the chromatic ink, the first 13 nozzles of the 15 nozzles of each color are used. For black ink, only 13 nozzles at the same sub-scanning position as the cyan use nozzles # C1 to # C13 are used. Thus, if the same number of nozzles are used for each of the four inks, the dots of each ink can be formed without omission or duplication by performing scanning according to the scanning parameters common to the nozzles for each. it can.
[0071]
In the present specification, the nozzle group for each ink composed of the nozzles used is also referred to as a “used nozzle group”. Further, the nozzle group for each ink provided in the actuator 40 is also referred to as a “mounting nozzle group”.
[0072]
As the use nozzles of the respective inks, those that are continuously arranged at the nozzle pitch k are selected. The interval between the lower nozzle # Y13 of the yellow nozzle group and the upper nozzle # M1 of the magenta nozzle group is 4k (ie, 24 dots). Similarly, the interval between the nozzle # M13 at the lower end of the magenta use nozzle group and the nozzle # C1 at the upper end of the cyan use nozzle group is also 4k.
[0073]
FIG. 9 is an explanatory diagram illustrating nozzles that record each raster line within the effective recording range in each pass of the first embodiment. In pass 1, the three nozzles # C11 to # C13 for cyan execute dot recording on the first, seventh, and thirteenth effective raster lines, respectively. The “effective raster line” means a raster line within the effective recording range. In FIG. 9, the leading sign “#” of the nozzle number is omitted. In addition, the hatched nozzles indicate unused nozzles. The symbol “x” indicates a position where there is no intermediate nozzle between adjacent mounting nozzle groups.
[0074]
In pass 2, the recording target position of the actuator 40 on the printing paper is moved from pass 1 by 13 dots in the sub-scanning direction. In this embodiment, since the nozzle pitch k is 6, the offset F of the nozzle position after the sub-scan feed (the remainder obtained by dividing the cumulative value ΣL of the feed amount L by k) is 1 dot. Therefore, in pass 2, it appears that the raster line one line lower than the raster line that was recorded in pass 1 appears to be recorded. Of course, in reality, the lower 13 raster lines are to be recorded. In the first embodiment, since the sub-scan feed amount L is a constant value of 13 dots, each time a sub-scan feed is performed, the position of the raster line to be recorded moves downward one by one. appear.
[0075]
For cyan ink, as will be described below, the cumulative value of the sub-scan feed error is the largest at the position Cmis between the sixth and seventh raster lines. The sixth raster line is recorded in pass 6, while the seventh raster line is recorded in pass 1. Accordingly, the sub-scan feed is performed five times between the pass 1 for recording the seventh raster line and the pass 6 for recording the sixth raster line. Accordingly, five sub-scan feed errors are accumulated between the sixth and seventh raster lines. Similarly, five sub-scan feed errors are accumulated for cyan ink between the 12th and 13th raster lines.
[0076]
From the same consideration as described above, it is understood that the accumulated value of the sub-scan feed error is relatively large for the magenta ink at the position Mmis between the seventh and eighth raster lines. For yellow ink, the accumulated value of the sub-scan feed error is relatively large at the position Ymis between the ninth and tenth raster lines. Hereinafter, a position where the accumulated value of the sub-scan feed error is relatively large is referred to as an “error accumulated position”.
[0077]
As can be understood from the above description, in the first embodiment, the error accumulation position differs for each chromatic color ink and does not match. At the error accumulation position, banding (striped image quality degradation portion extending in the main scanning direction) tends to occur. However, according to the present embodiment, since the error accumulation position is different for each chromatic ink, banding at these positions can be made inconspicuous.
[0078]
FIG. 10 is an explanatory diagram showing an actuator used in the first comparative example. In the actuator 40 ', each chromatic nozzle group 40Y', 40M ', 40C' is composed of 13 nozzles. Further, the interval between the nozzles at the end of each chromatic color nozzle group 40Y ′, 40M ′, 40C ′ is equal to the nozzle pitch k. That is, in the actuator 40 ′ of FIG. 10, the 13 nozzles for each chromatic color ink used in the first embodiment are continuously arranged at the nozzle pitch k. The black nozzle group 40K ′ is also composed of 39 nozzles arranged at the nozzle pitch k. In the first comparative example, such an actuator 40 'is used, and printing is executed according to the same scanning parameters as the scanning parameters of the first embodiment shown in FIG.
[0079]
FIG. 11 is an explanatory diagram showing nozzles that record each raster line in the effective recording range in each pass of the first comparative example. In the first comparative example, the error accumulation positions Cmis, Mmis, and Ymis for the three chromatic inks are positions between the sixth and seventh raster lines and positions between the twelfth and thirteenth raster lines. Match. In such a case, banding is conspicuous and image quality is likely to deteriorate.
[0080]
As can be understood by comparing the used nozzles shown in FIGS. 8 and 10, the difference between the first embodiment and the first comparative example is only the interval between the used nozzle groups. That is, in the first embodiment, the interval between the used color nozzle groups is set to a value 4k that is four times the nozzle pitch k, whereas in the first comparative example, the interval between the used nozzle groups is set to the nozzle. The same value as the pitch k is set. It can be understood that such a difference in the interval between the used nozzle groups appears as a difference in the generation positions of error accumulation positions Cmis, Mmis, and Ymis as shown in FIGS.
[0081]
In order to prevent the error accumulation positions of the adjacent nozzle groups along the sub-scanning direction as much as possible, in general, the interval between adjacent used nozzle groups is M times the nozzle pitch k (M is 2 or more). It is preferable to select the nozzle to be used so as to be an integer).
[0082]
However, it is preferable that the interval between the nozzle groups used along the sub-scanning direction is set as follows. FIG. 12 is an explanatory diagram showing equivalent nozzle positions in the printing method shown in FIG. As described with reference to FIG. 5, when the scan repetition number s is 1, one cycle of scanning includes k sub-scan feeds. Accordingly, the movement amount of the nozzle group in the sub-scan feed for one cycle is N × k raster. FIG. 12 shows the initial position of the nozzle group in each cycle from the first cycle to the third cycle. Since the same recording operation is executed from these three nozzle group positions, these positions are equivalent to each other. The interval between the lower end nozzle at the initial position of the first cycle and the upper end nozzle at the initial position of the second cycle is k dots. The interval between the lower end nozzle at the initial position of the first cycle and the upper end nozzle at the initial position of the third cycle is (N × k + k) dots. Although not shown, it can be seen that the interval between the lower end nozzle at the initial position of the first cycle and the upper end nozzle at the initial position of the fourth cycle is (2 × N × k + k) dots. In general, the interval between the lower end nozzle of the nozzle group at the initial position of the first cycle and the upper end nozzle of another equivalent nozzle group can be expressed as (N × n + 1) k dots. Here, n is an arbitrary integer of 0 or more.
[0083]
If the used nozzle groups of different inks are arranged at equivalent nozzle group positions as shown in FIG. 12, the error accumulation positions related to those inks coincide with each other. In order to avoid such a case, the interval between adjacent used nozzle groups should be set to a value other than (N × n + 1) k dots (N is the number of used nozzles, and n is an arbitrary integer greater than or equal to 1). Is preferred. Here, n is set to 1 or more instead of 0 or more, as described above, when the interval between adjacent used nozzle groups is set to M times the nozzle pitch k (M is an integer of 2 or more), n = This is because the case of 0 is excluded.
[0084]
The first embodiment described above further has the following features. As can be seen from FIG. 8 described above, the black nozzle row 40K precedes the color nozzle row during main scanning, and therefore, during color printing, black dots are formed on the printing paper prior to dots of other inks. Is done. Regarding the color nozzle row, the cyan nozzle group 40C, the magenta nozzle group 40M, and the yellow nozzle group 40Y are arranged in this order along the sub-scanning direction, and chromatic dots are formed in this order. . Further, only the nozzles present at the same sub-scanning position as the cyan use nozzle group existing at the rear end in the sub-scanning direction are used as the black use nozzle group.
[0085]
Due to the characteristics of the actuator 40 as described above, the following various advantages arise in the color printing of the first embodiment. The first advantage is that black dots are formed before dots of other inks. If a black dot is formed after another ink dot, the black ink is blurred and the saturation of the color image tends to decrease. In particular, when black ink and yellow ink ooze each other, they tend to decrease significantly again. Therefore, by selecting the nozzle group to be used as shown in FIG. 8, if the black dots are formed ahead of the dots of the other inks at an arbitrary position in the print area, the saturation of the color image is increased. Can be improved.
[0086]
A second advantage is that yellow dots are formed after dots of other inks at arbitrary positions in the print region. As can be understood from FIG. 8, when the printing paper P is conveyed in the sub-scanning direction, black dots and cyan dots are first formed in this order at any position in the printing area PA, and then magenta dots. Finally, yellow dots are formed. By the way, as shown in FIG. 4, after the trailing edge of the printing paper P passes through the nipping point of the first sub-scanning drive mechanism 25 (contact point of the rollers 25a and 25b), the sub-scan feed is relatively low accuracy. This is performed only by the second sub-scanning drive mechanism 27. As a result, as described below, when yellow dots are formed in a low precision region having the same width as the width WLP of the yellow nozzle group 40Y, the sub-scan feed is performed with relatively low precision. .
[0087]
FIG. 13 is an explanatory diagram showing the relationship between the low accuracy area LPA present at the trailing edge of the printing paper P and the actuator 40. When yellow dots are formed in the low-precision area LPA existing at the rear end of the print area PA, the second sub-scan driving mechanism 27 performs sub-scan feed with relatively low accuracy. Here, the “low accuracy area LPA” means an area where the sub-scan feed accuracy is low. The width of the low accuracy area LPA is equal to the width of the yellow nozzle group 40Y measured along the sub-scanning direction.
[0088]
At the time of FIG. 13, the formation of black dots, magenta dots, and cyan dots in the low accuracy area LPA has been completed. Accordingly, after the time point in FIG. 13, only yellow dots are formed in the low accuracy area LPA. In general, however, yellow dots are less noticeable than the other three color dots. For this reason, the sub-scan feed accuracy is low, and even if the position of the yellow dot is slightly shifted, the image quality is not deteriorated so much. That is, in this embodiment, when only the second sub-scanning drive mechanism 27 performs sub-scan feed, only yellow dots are formed in the low-precision area LPA, so that the image quality does not deteriorate much even in the low-precision area LPA. There is an advantage.
[0089]
By the way, in the vicinity of the leading edge and the trailing edge of the printing paper, printing is usually performed by a printing method different from that of the middle portion of the printing area. In this specification, the printing process in the vicinity of the rear end of the print area is referred to as “rear end process” or “lower end process”. Also, the printing process in the middle part of the printing area is called “intermediate process”. In the lower end process, the sub-scan feed is executed with a feed amount smaller than that in the middle portion of the print area so as not to excessively reduce the sub-scan feed accuracy. As the lower end processing, for example, there is a technique described in Japanese Patent Laid-Open No. 7-242025 disclosed by the present applicant. FIG. 9 of this publication shows that interlace printing is performed in the middle part of the print area, and that lower end processing is performed near the lower end of the print area by “minute feed” (one-dot sub-scan feed). Has been.
[0090]
In this embodiment, when yellow dots are formed in the low precision area LPA, the sub-scan feed is executed with the same feed amount as the intermediate process without performing the lower end process. Specifically, yellow dots are formed in the low accuracy area LPA using the sub-scan feed amount shown in FIG. 7 as it is. In other words, even when the sub-scan feed is executed only by the second sub-scan drive mechanism 27, the sub-scan feed is performed with the same feed amount as when the sub-scan feed by the first sub-scan drive mechanism 25 is executed. Execute. This has the advantage that the sub-scan feed control is simplified. Note that the yellow dots are less conspicuous than the other dots, so that the image quality does not deteriorate much even if the lower end processing is not performed.
[0091]
F. Second embodiment of the printing method:
FIG. 14 is an explanatory diagram showing scanning parameters in the printing method according to the second embodiment of the present invention. In the second embodiment, the nozzle pitch k is 6 dots, the scan repetition number s is 1, the number of used nozzles N is 15, and the effective nozzle number Neff is 15.
[0092]
In the table at the bottom of FIG. 14, parameters relating to the first to seventh passes are shown. As the sub-scan feed amount L, an array of three different values of 14, 15, and 16 dots is used. In this way, a printing method (scanning method) using an array of a plurality of different values as the sub-scan feed amount L is called “anomalous feed”. Note that the scanning parameters of the second embodiment also satisfy the above-described conditions c1 ′ to c3 ′.
[0093]
FIG. 15 is an explanatory diagram showing nozzles used in the second embodiment. The actuator 40 in FIG. 15 is the same as that shown in FIG. For chromatic ink, all 15 nozzles of each color are used. For black ink, only 15 nozzles at the same position in the sub-scanning direction as the cyan use nozzles # C1 to # C15 are used. Therefore, the interval between the lower nozzle # Y15 of the yellow nozzle group and the upper nozzle # M1 of the magenta nozzle group is 2k. Similarly, the distance between the nozzle # M15 at the lower end of the magenta use nozzle group and the nozzle # C1 at the upper end of the cyan use nozzle group is also 2k.
[0094]
Similar to the first embodiment described above, the second embodiment also has the following various advantages in color printing. The first advantage is that black dots are formed before dots of other inks, so that a color image with high saturation can be printed. The second advantage is that since only yellow dots are formed in the low accuracy area LPA (FIG. 13), the image quality does not deteriorate much even if the sub-scan feed accuracy is lowered. As in the first embodiment, when the sub-scan feed is executed only by the second sub-scan drive mechanism 27, the same feed as when the sub-scan feed by the first sub-scan drive mechanism 25 is executed. The sub-scan feed may be executed by the amount (that is, the feed amount shown in FIG. 14).
[0095]
FIG. 16 is an explanatory diagram illustrating nozzles that record each raster line within the effective recording range in each pass of the second embodiment. Since irregular feed is used in the second embodiment, the position of the nozzle group for each pass is not as regular as in the first embodiment. Therefore, there is an advantage that the accumulated sub-scan feed error is smaller than that in the first embodiment.
[0096]
The second embodiment also has an advantage that the accumulated error position of the sub-scan feed does not always coincide between the used nozzle groups, as will be described below. For cyan, the difference in the number of sub-scan feeds is the largest between the second and third raster lines, and the difference in the number of sub-scan feeds is 4. That is, for cyan, there is an error accumulation position Cmis between the second and third raster lines. Also for magenta and yellow, error accumulation positions Mmis and Ymis exist between the second and third raster lines. By the way, for cyan and magenta, the next accumulated error positions Cmis and Mmis exist between the eighth and ninth raster lines. On the other hand, for yellow, the next accumulated error position Ymis exists between the seventh and eighth raster lines.
[0097]
Thus, in the second embodiment, the accumulated error positions Cmis, Mmis, and Ymis for the three used nozzle groups do not always coincide. For this reason, compared to the case where the accumulated error positions Cmis, Mmis, and Ymis for the three used nozzle groups always coincide, the occurrence of banding due to the accumulated error of the sub-scan feed can be reduced.
[0098]
FIG. 17 is an explanatory diagram showing an actuator used in the second comparative example. In the actuator 40 ″ of FIG. 17, each of the chromatic nozzle groups 40Y ″, 40M ″, and 40C ″ is composed of 15 nozzles. Further, the interval between the nozzles at the ends of the chromatic nozzle groups 40Y ″, 40M ″, 40C ″ is equal to the nozzle pitch k. The black nozzle group 40 ″ is composed of 45 nozzles. . In the second comparative example, such an actuator 40 ″ is used, and printing is executed in accordance with the same scanning parameters as the scanning parameters of the second embodiment shown in FIG.
[0099]
FIG. 18 is an explanatory diagram illustrating nozzles that record each raster line within the effective recording range in each pass of the second comparative example. In the second comparative example, error accumulation positions Cmis, Mmis, and Ymis for the three chromatic inks are between the second and third raster lines, between the eighth and ninth raster lines, and the fourteenth. Between the 15th raster line. In other words, in the second embodiment, the error accumulation positions Cmis, Mmis, and Ymis for the three color inks always coincide with each other, and the error accumulation positions Cmis, Mmis, Ymis appears repeatedly. Thus, if the error accumulation positions Cmis, Mmis, and Ymis for each chromatic nozzle group are always matched, banding is easily noticeable.
[0100]
As can be seen by comparing FIG. 15 and FIG. 17, the difference between the second embodiment and the second comparative example is only the interval between the nozzle groups used. That is, in the second embodiment, the interval between the used nozzle groups is set to a value 2k that is twice the nozzle pitch k, whereas in the second comparative example, the interval between the used nozzle groups is set to the nozzle pitch k. It is set to the same value. Such a difference in the interval between the used nozzle groups appears as a difference in the generation positions of the error accumulation positions Cmis, Mmis, and Ymis as shown in FIGS.
[0101]
As will be understood from this, in the second embodiment, similarly to the first embodiment, the used nozzles are arranged so that the interval between adjacent used nozzle groups is M times the nozzle pitch k (M is an integer of 2 or more). Is selected. The interval between adjacent used nozzle groups is set to a value other than (N × n + 1) k dots (N is the number of used nozzles, and n is an arbitrary integer equal to or greater than 1).
[0102]
As can be understood from FIG. 15, in the second embodiment, all chromatic ink nozzles provided in the actuator 40 are used. In the actuator 40 used in this embodiment, the interval between the mounting nozzle groups of each ink is set to a value twice the nozzle pitch k. Therefore, even if all the chromatic color nozzles are used, the sub-scan feed is performed. The error accumulation position does not always coincide between the chromatic color nozzle groups. Therefore, there is an advantage that high-quality printing can be performed by using as many chromatic ink nozzles as possible among the nozzles provided in the actuator 40.
[0103]
In general, the interval between the mounting nozzle groups arranged along the sub-scanning direction (that is, the interval between the nozzles at the end of the mounting nozzle group for each ink) is m times the nozzle pitch k (m Is preferably set to be an integer of 2 or more. By doing so, it is possible to perform high-quality printing using as many nozzles as possible for the reasons described above.
[0104]
The interval between the mounting nozzle groups arranged along the sub-scanning direction may be set equal to the nozzle pitch k. In this case, if some of the nozzles in each mounting nozzle group are not used, it is possible to configure the same used nozzle group as in the first and second embodiments.
[0105]
G. Actuator variations:
FIG. 19 is an explanatory diagram illustrating a first modification of the actuator. The left nozzle row of the actuator 41 is the same as the left nozzle row of the actuator 40 of the embodiment shown in FIG. The right nozzle row of the actuator 41 in FIG. 19 includes a light magenta nozzle group 40LM, a light cyan nozzle group 40LC, and a black nozzle group 40K. Each ink mounting nozzle group includes 15 nozzles. The intervals between the mounting nozzle groups for the three colors arranged on a straight line in the sub-scanning direction are 2k.
[0106]
The light magenta ink has substantially the same hue as that of normal magenta ink, and has a lower density than normal magenta ink. The same applies to light cyan ink. The normal magenta ink and the normal cyan ink may be referred to as “dark magenta ink” and “dark cyan ink”.
[0107]
Even when the actuator 41 shown in FIG. 19 is used, color printing can be executed according to the same scanning parameters as when the actuator 40 shown in FIG. 3 is used. Further, when the same printing method as that in the first and second embodiments is adopted, the error accumulation positions of the three nozzle groups 40LM, 40LC, and 40K on the right side of FIG. can get.
[0108]
Note that the use of the actuator 41 shown in FIG. 19 has the advantage that the image quality of the color image can be improved compared to the actuator 40 shown in FIG. 3 because six-color printing can be performed using light ink. On the other hand, when the actuator 40 shown in FIG. 3 is used, black printing can be performed at a high speed because black ink nozzles about three times as many as the actuator 41 shown in FIG. 19 can be used during monochrome printing. There is an advantage that can be made.
[0109]
When the actuator 41 of FIG. 19 is used, yellow dots and light magenta in the low accuracy area LPA after the time point shown in FIG. 13 (that is, when the sub-scan feed is performed only by the second sub-scan driving mechanism 27). Dots are formed. However, since light magenta dots are relatively inconspicuous like yellow dots, the image quality does not deteriorate much even if the accuracy of sub-scan feed is low. Accordingly, even when the actuator 41 shown in FIG. 19 is used, when the sub-scan feed is executed only by the second sub-scan drive mechanism 27, the sub-scan feed by the first sub-scan drive mechanism 25 is executed. The sub-scan feed may be executed with the same feed amount.
[0110]
As can be understood from the example of FIG. 19, when the sub-scan feed is performed only by the second sub-scan driving mechanism 27, only dots of ink having a relatively low density are formed in the low accuracy area LPA. It is preferable to do so. Here, “relatively low density ink” means yellow ink when only four color inks of CMYK are available, and when dark ink and light ink are available. Means light ink (for example, light cyan or light magenta) and yellow ink.
[0111]
FIG. 20 is an explanatory diagram illustrating a second modification of the actuator. This actuator 42 exchanges the positions of the dark magenta nozzle group 40M and the light magenta nozzle group 40LM of the actuator 41 of the first modified example shown in FIG. 19, and the dark cyan nozzle group 40C and the light cyan nozzle group 40LM. The position of the nozzle group 40LC is exchanged. This actuator 42 also has substantially the same advantages as the actuator 41 shown in FIG.
[0112]
However, when the actuator 42 of FIG. 20 is used, yellow dots and dark magenta dots are formed in the low accuracy area LPA after the time point shown in FIG. Accordingly, the actuator 41 shown in FIG. 19 is preferable to the actuator 42 shown in FIG. 20 in terms of image quality in the low accuracy area LPA.
[0113]
FIG. 21 is an explanatory diagram showing a third modification of the actuator. In this actuator 43, the color nozzle rows and the black nozzle rows 40K of the actuator 40 of the embodiment shown in FIG. 3 are arranged in two rows in a staggered manner. For example, in the black nozzle row 40K, odd-numbered nozzles # K1, # K3... # K47 are arranged in the left column, and even-numbered nozzles # K2, # K4. Similarly, in the three chromatic nozzle groups 40Y, 40M, and 40C, the nozzles are arranged in a staggered manner. Thus, even when the nozzles are arranged in a staggered manner, the three chromatic nozzle groups 40Y, 40M, and 40C are arranged in a straight line along the sub-scanning direction. That is, in this specification, the phrase “a plurality of nozzle groups are arranged in a straight line along the sub-scanning direction” is only necessary that the nozzle groups are arranged in a straight line as a whole. The plurality of nozzles constituting the nozzle group are not necessarily arranged in a straight line.
[0114]
In the actuators shown in the various embodiments and modifications described above, the nozzles for four colors or six colors are arranged in two rows. However, these nozzles may be arranged in one row. It may be arranged in a plurality of rows more than the row. For example, a group of four colors of nozzles may be arranged in a row by providing 15 black nozzles with an interval of 2k below the color nozzle group of FIG.
[0115]
It is also possible to use a print head in which the interval between the nozzle groups of each color is set to the same value as the nozzle pitch k.
[0116]
FIG. 22 is an explanatory view showing a fourth modification of the actuator. In the fourth modification example, two actuators are used: a first actuator 44a including only the color nozzle row and a second actuator 44b including only the black nozzle row 40K. The nozzle groups for each color are arranged in a staggered manner as in FIG. The only difference from FIG. 21 is that the color ink nozzle groups each have 16 nozzles, and the interval between the color ink nozzle groups is equal to the nozzle pitch k.
[0117]
FIG. 23 is an explanatory diagram showing a fifth modification of the actuator. The actuator 45 includes three color nozzle rows and one black nozzle row. The first color nozzle row is composed of a yellow nozzle group 40Y and a magenta nozzle group 40M. The second color nozzle row is composed of a light magenta nozzle group 40LM and a cyan nozzle group 40C. The third color nozzle row is composed of a light cyan nozzle group 40LC and a light black nozzle group 40LK.
[0118]
The nozzle groups are arranged in a straight line along the sub-scanning direction, but can be arranged in a staggered manner as shown in FIGS. The black nozzle row 40K has 48 nozzles. Each nozzle group other than the black nozzle row 40K has 24 nozzles. Even when this actuator 45 is used, printing can be performed so that only dots of ink (yellow, light magenta, and light cyan) having a relatively low density are formed in the low accuracy area LPA. Does not decrease much.
[0119]
FIG. 24 is an explanatory diagram showing a sixth modification of the actuator. The actuator 46 also includes three color nozzle rows and one black nozzle row. Since the difference between the actuator 46 and the actuator 45 shown in FIG. 21 is only the position of the nozzle group other than the black nozzle row 40K and the yellow nozzle group 40Y, detailed description thereof is omitted.
[0120]
FIG. 25 is an explanatory diagram showing a seventh modification of the actuator. The actuator 47 has three nozzle rows. The first nozzle row is composed of a yellow nozzle group 40Y and a magenta nozzle group 40M. The second nozzle row includes a light magenta nozzle group 40LM and a cyan nozzle group 40C. The third nozzle row is composed of a light cyan nozzle group 40LC and a black nozzle group 40K. Even when this actuator 46 is used, as in the case of FIG. 23, since printing can be performed so that only dots of ink having a relatively low density are formed in the low-precision area LPA, the image quality is greatly deteriorated. There is nothing to do.
[0121]
FIG. 26 is an explanatory diagram showing an eighth modification of the actuator. The actuator 48 is a group of nozzles for six colors arranged in a line in the sub-scanning direction. Each nozzle group has eight nozzles. It is also possible to arrange the nozzle groups for each ink in a staggered manner. Even when this actuator 47 is used, printing can be performed such that only yellow ink dots are formed in the low-precision area LPA, so that the image quality does not deteriorate so much.
[0122]
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0123]
(1) In the above embodiment, only the case where the scan repetition number s is 1 has been described, but the present invention can also be applied to the case where the scan repetition number s exceeds 1.
[0124]
(2) Some printing apparatuses can set the dot pitch (recording resolution) in the main scanning direction and the dot pitch in the sub-scanning direction to different values. In this case, parameters related to the main scanning direction (for example, pixel pitch on the raster line) are defined by dot pitches in the main scanning direction, while parameters related to the sub scanning direction (for example, nozzle pitch k and sub scanning). The feed amount L) is defined by the dot pitch in the sub-scanning direction.
[0125]
(3) The present invention is also applicable to a drum scan printer. In the drum scan printer, the drum rotation direction is the main scanning direction, and the carriage traveling direction is the sub-scanning direction. The present invention can be applied not only to an ink jet printer but also to a printing apparatus that generally records on the surface of a print medium using a print head having a plurality of dot forming element arrays. Here, “dot forming element” means a component for forming dots, such as an ink nozzle in an ink jet printer. Examples of such a printing apparatus include a facsimile machine and a copying machine.
[0126]
(4) In the above embodiment, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced with hardware. Also good. For example, the host computer 100 can execute part of the functions of the system controller 54 (FIG. 2).
[0127]
A computer program for realizing such a function is provided in a form recorded on a computer-readable recording medium such as a floppy disk or a CD-ROM. The host computer 100 reads the computer program from the recording medium and transfers it to an internal storage device or an external storage device. Alternatively, the computer program may be supplied from the program supply device to the host computer 100 via a communication path. When realizing the function of the computer program, the computer program stored in the internal storage device is executed by the microprocessor of the host computer 100. Further, the host computer 100 may directly execute the computer program recorded on the recording medium.
[0128]
In this specification, the host computer 100 is a concept including a hardware device and an operation system, and means a hardware device that operates under the control of the operation system. The computer program causes the host computer 100 to realize the functions of the above-described units. Note that some of the functions described above may be realized by an operation system instead of an application program.
[0129]
In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, An external storage device fixed to a computer such as a hard disk is also included.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a main configuration of a color inkjet printer 20 as an embodiment of the present invention.
FIG. 2 is a block diagram showing an electrical configuration of the printer 20;
FIG. 3 is an explanatory diagram showing an arrangement of nozzles formed on the bottom surface of the actuator 40;
FIG. 4 is a side sectional view showing a sub-scanning drive mechanism that conveys printing paper P.
FIG. 5 is an explanatory diagram for illustrating basic conditions of a general dot recording method when the scan repetition number s is 1. FIG.
FIG. 6 is an explanatory diagram for illustrating basic conditions of a general dot recording method when the number of scan repetitions s is 2 or more.
FIG. 7 is an explanatory diagram showing scanning parameters in the printing method according to the first embodiment of the present invention.
FIG. 8 is an explanatory diagram showing nozzles used in the first embodiment.
FIG. 9 is an explanatory diagram illustrating nozzles that record each raster line within an effective recording range in each pass of the first embodiment.
FIG. 10 is an explanatory diagram showing nozzles used in the first comparative example.
FIG. 11 is an explanatory diagram illustrating nozzles that record each raster line within an effective recording range in each pass of the first comparative example.
FIG. 12 is an explanatory diagram showing equivalent nozzle positions.
13 is an explanatory diagram showing a relationship between a low-precision area LPA present at the rear end of the printing paper P and the actuator 40. FIG.
FIG. 14 is an explanatory diagram showing scanning parameters in the printing method according to the second embodiment of the present invention.
FIG. 15 is an explanatory diagram showing nozzles used in the second embodiment.
FIG. 16 is an explanatory diagram illustrating nozzles that record each raster line within an effective recording range in each pass of the second embodiment.
FIG. 17 is an explanatory diagram showing nozzles used in a second comparative example.
FIG. 18 is an explanatory diagram illustrating nozzles that record each raster line within the effective recording range in each pass of the second comparative example.
FIG. 19 is an explanatory diagram showing a first modification of the actuator.
FIG. 20 is an explanatory diagram showing a second modification of the actuator.
FIG. 21 is an explanatory diagram showing a third modification of the actuator.
FIG. 22 is an explanatory diagram showing a fourth modification of the actuator.
FIG. 23 is an explanatory view showing a fifth modification of the actuator.
FIG. 24 is an explanatory view showing a sixth modification of the actuator.
FIG. 25 is an explanatory diagram showing a seventh modification of the actuator.
FIG. 26 is an explanatory view showing an eighth modification of the actuator.
FIG. 27 is an explanatory diagram showing an example of an interlace recording method.
FIG. 28 is an explanatory diagram showing an example of an overlap recording method.
[Explanation of symbols]
20 ... Color inkjet printer
22 ... Paper stacker
24. Paper feed roller
25. First sub-scanning drive mechanism
25a: paper feed roller
25b ... driven roller
26 ... Platen plate
27. First sub-scanning drive mechanism
27a: paper discharge roller
27b ... Giza Roller
28 ... Carriage
30 ... Carriage motor
31 ... Paper feed motor
32 ... Traction belt
34 ... Guide rail
36 ... Print head
40 ... Actuator
50: Receive buffer memory
52 ... Image buffer
54 ... System controller
61 ... Main scanning driver
62 ... Sub-scanning driver
63: Head drive driver
100: Host computer

Claims (12)

A printing apparatus that prints an image by recording dots on the surface of a print medium,
A print head including a plurality of dot forming elements for forming dots on the print medium;
A main scanning drive unit that performs main scanning by driving at least one of the print head and the print medium;
A head drive unit that drives at least a part of a plurality of dot formation elements included in each dot formation element array during the main scanning to form dots;
A sub-scan driving unit that performs sub-scanning by driving at least one of the print head and the print medium every time the main scanning is completed;
A control unit for controlling the respective units,
The sub-scanning drive unit
A first sub-scanning drive mechanism that performs sub-scan feed with relatively high accuracy;
A second sub-scanning driving mechanism that performs sub-scanning feeding with relatively low accuracy after at least sub-scanning feeding by the first sub-scanning driving mechanism is completed;
With
The print head has a plurality of dot-forming element groups for forming a yellow dot forming element groups at least unrealized different colored dots for forming yellow dots, arranged in a predetermined order in the sub-scanning direction A first dot forming element array,
In the first dot formation element array, the arrangement order of the plurality of dot formation element groups is such that yellow dots are formed after other dots at any position on the print medium during color printing. And the plurality of dot forming element groups each include an equal number of dot forming elements,
In the print head, the plurality of dot forming elements are arranged so that yellow dots are formed after black dots, magenta dots, and cyan dots at arbitrary positions on the print medium during color printing. And
The controller is
During color printing,
Formation of the black dots, magenta dots, and cyan dots on the print medium while performing the sub-scan feed with the relatively high accuracy using both the first and second sub-scan driving mechanisms And complete
The black dot, the magenta dot, and the cyan when the sub-scan feed is executed only by the second sub-scanning drive mechanism after the trailing edge of the print medium has passed the clamping point of the first sub-scanning drive mechanism. Among the dot forming elements included in the first dot forming element array in the region where the dot formation is completed and the yellow dot formation is not completed , the dot forming elements included in the yellow dot forming element group A printing apparatus that performs printing using only the printer. The printing apparatus according to claim 1,
The controller is
When the rear end of the print medium passes through the clamping point of the first sub-scanning drive mechanism and the sub-scan feed is executed only by the second sub-scanning drive mechanism , the rear end of the print medium is The second sub-scanning drive mechanism is fed to the second sub-scanning drive mechanism with the same feed amount as when the first sub-scanning drive mechanism is executed at a position before passing the clamping point of the first sub-scanning drive mechanism. A printing device that performs scanning feed. The printing apparatus according to claim 1, wherein:
The print head further comprises:
A black dot forming element group for forming black dots is formed in parallel with the first dot forming element array, and is formed on the print medium prior to the first dot forming element array. A second dot forming element array capable of forming dots,
The black dot formation element group has at least a plurality of dot formation elements arranged at the same sub-scanning position as the dot formation elements included in the plurality of dot formation element groups in the first dot formation element array. And
The controller is
During color printing, with respect to black dots, a specific chromatic color that enables dot formation on the printing medium to be executed earliest among the plurality of dot formation element groups in the first dot formation element array. A printing apparatus that forms black dots using only dot forming elements existing at the same sub-scanning position as dot forming elements used in a dot forming element group. The printing apparatus according to any one of claims 1 to 3,
The printing apparatus, wherein the first and second dot forming element arrays are formed in the same actuator. A printing method for printing an image by recording dots on the surface of a print medium using a printing apparatus,
(A) As a printing device,
A first sub-scanning drive mechanism that performs sub-scan feed with relatively high accuracy;
A second sub-scanning driving mechanism that performs sub-scanning feeding with relatively low accuracy after at least sub-scanning feeding by the first sub-scanning driving mechanism is completed;
A step of preparing a printing device comprising a print head;
(B) a step of performing color printing using the printing apparatus,
The print head has a plurality of dot-forming element groups for forming a yellow dot forming element groups at least unrealized different colored dots for forming yellow dots, arranged in a predetermined order in the sub-scanning direction A first dot forming element array,
In the first dot formation element array, the arrangement order of the plurality of dot formation element groups is such that yellow dots are formed after other dots at any position on the print medium during color printing. And the plurality of dot forming element groups each include an equal number of dot forming elements,
In the print head, the plurality of dot forming elements are arranged so that yellow dots are formed after black dots, magenta dots, and cyan dots at arbitrary positions on the print medium during color printing. And
In the color printing in the step (b),
Formation of the black dots, magenta dots, and cyan dots on the print medium while performing the sub-scan feed with the relatively high accuracy using both the first and second sub-scan driving mechanisms And complete
The black dot, the magenta dot, and the cyan when the sub-scan feed is executed only by the second sub-scanning drive mechanism after the trailing edge of the print medium has passed the clamping point of the first sub-scanning drive mechanism. Among the dot forming elements included in the first dot forming element array in the region where the dot formation is completed and the yellow dot formation is not completed , the dot forming elements included in the yellow dot forming element group A printing method characterized in that printing is executed using only The printing method according to claim 5, comprising:
The step (b)
When the rear end of the print medium passes through the clamping point of the first sub-scanning drive mechanism and the sub-scan feed is executed only by the second sub-scanning drive mechanism , the rear end of the print medium is A printing method in which sub-scan feed is executed with the same feed amount as when sub-scan feed by the first sub-scan drive mechanism is executed at a position before passing the clamping point of the first sub-scan drive mechanism. The printing method according to claim 5 or 6, comprising:
The print head further comprises:
A black dot forming element group for forming black dots is formed in parallel with the first dot forming element array, and is formed on the print medium prior to the first dot forming element array. A second dot forming element array capable of forming dots,
The black dot formation element group has at least a plurality of dot formation elements arranged at the same sub-scanning position as the dot formation elements included in the plurality of dot formation element groups in the first dot formation element array. And
The step (b)
As for black dots, it is used in a specific chromatic color dot forming element group that can execute dot formation on the printing medium earliest among the plurality of dot forming element groups in the first dot forming element array. A printing method in which black dots are formed using only dot forming elements existing at the same sub-scanning position as the dot forming elements to be formed. In order to print an image by recording dots on the surface of a printing medium, a first sub-scanning drive mechanism that performs sub-scan feed with relatively high accuracy, and a sub-scan feed by at least the first sub-scanning drive mechanism Is a print head used in a printing apparatus provided with a second sub-scanning drive mechanism that performs sub-scan feed with relatively low accuracy after
The plurality of dot-forming element groups for forming at least unrealized different colored dots yellow dot forming element groups for forming the yellow dots, arranged in a predetermined order along a predetermined sub-scanning direction 1 dot-forming element array,
The plurality of dot forming element groups in the first dot forming element array each include an equal number of dot forming elements,
In the first dot formation element array, the arrangement order of the plurality of dot formation element groups is such that yellow dots are formed after other dots at an arbitrary position on the print medium during color printing. And the plurality of dot forming element groups each include an equal number of dot forming elements,
In the print head, the plurality of dot forming elements are arranged so that yellow dots are formed after black dots, magenta dots, and cyan dots at arbitrary positions on the print medium during color printing. And
The first dot forming element array includes the black on the print medium while performing the sub-scan feed with the relatively high accuracy using both the first and second sub-scan driving mechanisms. After the formation of dots, magenta dots, and cyan dots is completed , sub-scan feed is performed only by the second sub-scanning drive mechanism after the trailing edge of the print medium has passed the clamping point of the first sub-scanning drive mechanism. When executed, the dot formation elements included in the first dot formation element array in a region where the formation of the black dots, magenta dots, and cyan dots is completed and the formation of the yellow dots is not completed . Among them, the print head is arranged so that only dot forming elements included in the yellow dot forming element group are used. The print head of claim 8, further comprising:
A second dot forming element array that is arranged in parallel with the first dot forming element array and includes a group of black dot forming elements for forming black dots;
The black dot forming element group is a print head arranged at an end opposite to an end where the yellow dot forming element group is arranged. The print head according to claim 9, comprising:
The first and second dot forming element arrays each include a same number of dot forming element groups for forming dots of different colors. The print head according to claim 9, comprising:
The print head, wherein the second dot formation element array includes black dot formation elements arranged at the same sub-scanning position as the dot formation elements included in the first dot formation element array. The print head according to any one of claims 9 to 11,
The print head, wherein the first and second dot forming element arrays are formed in the same actuator.

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